Vestibulospinal Tract

Original Editor - Kate Sampson

Top Contributors - Kate Sampson, Lucinda hampton, Wendy Walker, WikiSysop and Kim Jackson

Introduction[edit | edit source]

Vestibulospinal tract

Vestibulospinal tracts are descending tracts present in the spinal cord, ie a bundle of nerve fibers that carry information from the higher centers of the brain to the peripheral parts of the body.

They begins with the axons of the vestibular nuclei (within the brainstem) and terminates by synapsing with the interneurons present in the anterior gray column of the spinal cord. The vestibulospinal tracts consist of a medial vestibulospinal tract and a lateral vestibulospinal tract. They are essential for a number of reflex actions performed by the body[1].

Each tract is responsible for increasing antigravity muscle tone in response to the head being tilted to one side. Antigravity muscles are extensor muscles in the limbs[2]

Part of the Extrapyramidal system.

Anatomy[edit | edit source]

Lateral Vestibulospinal Tract

  • Origin: Lateral vestibular nucleus within brainstem [2]
  • Course: Fibres descend ipsilaterally though the anterior funiculus of the same side of the spinal cord, synapsing on the extensor antigravity motor neurons.[2][3]

Medial Vestibulospinal Tract

  • Origin: Medial and inferior vestibular nuclei[2]
  • Course: Descends bilaterally in the medial longitudinal fasciculus. Synapses with the excitatory and inhibitory neurons of the cervical spine. [2]
  • Innervates interneurons in the cervical and upper thoracic spine. [4]

Functions[edit | edit source]

2C Vestibular spinal tract

Upright Posture Maintenance: Performed by both the medial and the lateral vestibulospinal tracts. The medial tract supplies the muscles of the head and neck whereas the lateral tract supplies the muscles located in other parts of the body. When the head of the person moves, signals are sent by these vestibular tracts to specific antigravity muscles. These muscles contract and maintain the upright posture of the body.

Vestibulospinal Reflexes: A vestibulospinal reflex is the one that uses organs of the vestibular system and the skeletal muscles in order to maintain balance and posture[1]. See more here Vestibular Anatomy and Neurophysiology, were the reflexes are explained

Medial Vestibulospinal Tract

Vestibulo-ocular reflex lateroflexion of neck

Head and Eye Coordination: Performs the synchronization of the movement of the eyes with the movement of the head so that eyes do not lag behind when the head moves to one side. This function is very important for maintaining the balance of the body.

Head righting reflexes. These are responsible for keeping the head and gaze horizontal

Eye righting reflex (Vestibulo-ocular reflex) This origniates in the ascending medial longitudinal fasciulus and extends to the extraocular muscles of the eyes. The horizonal position of the eyes when the head is an upright postural set is caused by cancelling of the tonic acitiy of the deiteroocular pathways.[2] It is therefore able to keep the eyes still while the head moves, allowing images to focus on the retina [4]

Pathology[edit | edit source]

The vestibulospinal tracts can be damaged by injury or diseases of the spinal cord. Including:

  • Ataxia, the person is unable to maintain his balance, especially when the eyes are closed. It is due to the loss of vestibulospinal reflexes.
  • Hypermetria, ataxia in which movements overreach the intended goal. [5]
  • Postural Instability, the person is unable to maintain an upright posture. The patient will not be able to maintain posture while walking and will fall on the affected side.[5]
  • Damage to the medial vestibulospinal tract will result in nystagmus [1]

Animal studies have suggested that there is an underlying balance  between descending systems controlling stretch reflex activity: the dorsal reticulospinal tract (inhibitory) and the facilitatory medial reticulospinal and vestibulospinal tract (facilitatory).[6] If this is impaired it could cause further symptoms of the upper motor neurone syndrome.

Impairment to the medial vestibulospinal tract is also suggested to impair the vestibular-evoked myogenic potential resulting in spontaneous nystagmus, gaze-evoked nystagmus and tilt of the subjective visual vertical [7]

References[edit | edit source]

  1. 1.0 1.1 1.2 Brain made simple Vestibulospinal tracts Available: 27.4.2022)
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Fitzgerald MJT, Gruener G, Mtui E. Clinical Neuroanatomy and Neuroscience. Fifth Edition. Philadelphia:Elsevier Saunders, 2007
  3. Crossman AR, Neary D. Neuroanatomy. An illustrated colour text. Third Edition. Philadelphia:Elsevier ,2005
  4. 4.0 4.1 Gjelsvik BEB. The Bobath Concept in Adult Neurology. Germany: Thieme, 2008
  5. 5.0 5.1 Horak FB. Postural Compensation for Vestibular Loss. Ann N Y Acad Sci 2009; 1164: 76–81.
  6. Trompetto C, Marinelli L, Mori L,Pelosin E, Currà A, Molfetta L, Abbruzzese1 G. Pathophysiology of Spasticity: Implications for Neurorehabilitation. BioMed Research International 2014;
  7. Kim S, Lee HS, Kim JS. Medial vestibulospinal tract lesions impair sacculo-collic reflexes. Journal of Neurology 2010; 257:5: 825-832